With the civilization of society, there is growing concern over sanitation in daily life. A notable example is public baths for nondiscriminatory use by ordinary people. To rapidly remove residual water on the hands of a user after the user washes the hands, hand-wiping paper (towels) is usually provided at public baths. As people have increasing awareness of environmental protection and pay careful attention to forestry resources, it becomes increasingly evident that disposable paper (towels) is not practical. Therefore, hand dryers become popular and are widely disposed at public places to meet people's requirements of rapid hand drying.
In view of this, after the high economic development in the last century, people are concentrated in urban areas and many huge cities appear. People usually strive for speed and efficiency. At present, accordingly, a main objective of commercially available hand dryers is to improve the efficiency of hand drying. A major difficulty in the industrial design of the hand dryers is to work out a compromise between efficiency and noise. It should be known that in the process of continuously accelerating the operation of a motor to supply air, during extraction of air, friction occurs between related mechanisms of the hand dryer inevitably to generate wind noise. If the rotational speed of the motor is deliberately reduced to reduce the wind noise in the operation of the hand dryer, a working time of the hand dryer needs to be increased to dry hands thoroughly.
A common point between the technologies disclosed in US Patent No. 20130111778 and China Patent No. 201194769 lies in that: The hand dryer includes a motor and an air path structure. The air path structure includes an air inlet and a plurality of water-retaining sheets disposed at the air inlet. A gap is formed between one of the plurality of water-retaining sheet and another adjacent water-retaining sheet. When the hand dryer is working, air enters the air path structure through the gaps. Because of a smoother air path, noise generated during working can be reduced.
In addition, a hand dryer shown in China Patent No. 105919494 includes a housing and a motor disposed inside the housing. A first air inlet is disposed on the housing. The motor includes a second air inlet and an air intake channel connected to the first air inlet and the second air inlet. The air intake channel includes a baffle disposed in the air intake channel and a gap that is defined by the baffle and the inner wall of the air intake channel. The baffle is used to reflect noise that is generated when the motor is running and propagates externally along the air intake channel. Through the gap, an air flow disperses first and then gathers, so as to produce a flow-regulation effect and reduce noise generated from the air flow.
However, when only a blower structure is improved, it is still difficult to reach the extreme objective of being “super-silent”. Therefore, how to work out a compromise between efficiency and noise for the purpose of noise reduction is in fact a major topic in the industrial design in this technical field.